Allocate memory to dynamically growing char array in C throws segmentation fault

Question

I have created a custom type (type def) in C,a dynamic char array, but I receive the segmentation fault error when I try to initialize this type def using malloc. The following code is a code snippet of my structure and its implementation:

#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>

typedef struct {
  char * list;
  size_t used;
  size_t size;
} CharList;

void initCharList(CharList *l) {
  size_t initialSize = 10;
  l->list = (char*)malloc(10+1 * sizeof(char)); 
  l->used = 0;
  l->size = initialSize;
}

void appendStringCharList(CharList *l, char elements[], int arr_length) {
  if (l->used + arr_length >= l->size) {
    l->size += arr_length;
    l->list = realloc(l->list, l->size * sizeof(char *));
  }
  for (int i = 0; i < arr_length; i++) {
    l->list[l->used++] = elements[i];
  }
}

struct Lexer {
  CharList * text;
  int position;
  char currentChar;
};

void advanceLexer(struct Lexer * lexer) {
  lexer->position +=1;
  lexer->currentChar = (char) ((lexer->position < lexer->text->used) ? lexer->text->list[lexer->position] : '\0');
}

void createLexer(struct Lexer * lexer, char text[], int arrLength) {
  initCharList(lexer->text);
  appendStringCharList(lexer->text, text, arrLength);
  lexer->position = -1;
  advanceLexer(lexer);
}

int main(void) {
  struct Lexer lexer;
  char myCharArr[] = "1234567890";
  createLexer(&lexer, myCharArr, 11);
  return 0;
}

Incomplete code snippets are not enough. Please provide a complete minimal reproducible example. — kaylum
– kaylum, Commented Jul 9, 2021 at 1:12
Also, do basic debugging. Run your program in a debugger. That will give you the exact line of code that triggers the seg fault and more. — kaylum
– kaylum, Commented Jul 9, 2021 at 1:13
That is still not a complete example. Please read the link. We need to have code that anyone can copy exactly as shown to run and see the problem. — kaylum
– kaylum, Commented Jul 9, 2021 at 1:20
i edited, the code is a little bit expensive and i have tried to minify — José Thomaz
– José Thomaz, Commented Jul 9, 2021 at 1:37

Ken Y-N · Accepted Answer · 2021-07-09 01:46:21Z

1

struct Lexer {
  CharList * text;
  int position;
  char currentChar;
};

You do not allocate CharList * text;; the simplest fix is:

struct Lexer {
  CharList text;
  int position;
  char currentChar;
};

answered Jul 9, 2021 at 1:46

Ken Y-N

15.2k22 gold badges80 silver badges122 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

José Thomaz Over a year ago

thanks, this solved my problem, but you could explain me why? I did not understand why just removing the pointer has fixed all

Collectives™ on Stack Overflow

Allocate memory to dynamically growing char array in C throws segmentation fault

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related